The giant diverticulum of the colon is a rare entity first diagnosed by Bouvin and Bonte in 1946. Few cases have been reported in the literature. It is normally located in the antimesenteric border of the sigmoid colon. In most cases it is considered to be an uncommon complication of a common disease: colonic diverticulosis. We present a case of giant diverticulum of the sigma diagnosed in an 80-year-old man and we describe the plain-film and CT findings.